This application claims the priority of the commonly owned copending German patent application Serial No. 101 31 221.0 filed Jun. 28, 2001. The disclosure of the aforesaid copending patent application, as well as that of each US and foreign patent and patent application identified in the specification of the present application, is incorporated herein by reference.
The present invention relates to improvements in apparatus for actuating cutches, and more particularly to improvements in fluid-operated apparatus for engaging and/or disengaging clutches in the power trains of motor vehicles. Apparatus of the type to which the present invention pertains are known as concentric or central fluid-operated (such as hydraulic) clutch actuating apparatus.
Certain presently known clutch actuating apparatus employ a slave cylinder having a housing which is coaxial with the input shaft of the change-speed transmission, which confines a reciprocable piston, and which is separably affixed to the housing or case of the transmission. The piston is a hollow cylindrical body which is reciprocable in the slave cylinder housing and surrounds a stationary hollow cylindrical guide which, in turn, surrounds and is spaced apart from the adjacent portion of the input shaft of the transmission. One end portion of the cylindrical guide is provided with a flange or collar which is confined between the slave cylinder housing and the adjacent end portion of the transmission case. One end portion of the piston of the slave cylinder is provided with an annular sealing element which is disposed at one axial end of a plenum chamber and sealingly engages the internal surface of the slave cylinder housing as well as the external surface of the hollow cylindrical guide. The other end portion of the piston mounts a clutch release bearing which can actuate the friction clutch, e.g., by pivoting a set of prongs or tongues provided on a diaphragm spring which can displace a reciprocable pressure plate in the housing of the friction clutch. When the clutch is at least partially engaged, it can transmit torque between an output element of the prime mover (such as an internal combustion engine or a hybrid drive) and the input shaft of the transmission. The release bearing can actuate the clutch in response to admission of a pressurized fluid (e.g., oil) into the plenum chamber; such fluid can be admitted into or evacuated from the plenum chamber by way of one or more passages in the housing of the slave cylinder, e.g., by way of a radially extending nipple which is affixed to or is of one piece with the housing of the slave cylinder.
A clutch actuating apparatus of the just outlined character is disclosed, for example, in German patent application Serial No. 43 13 346. The housing of the slave cylinder in the apparatus of this German patent application comprises two tubular sections which are made of sheet metal and one of which surrounds the other. One end portion of the outer section is sealingly and non-separably affixed to one end portion of the inner section and is attached to the case of the change-speed transmission. These sections define an annular plenum chamber which can receive pressurized fluid by way of a conduit one end portion of which is received in a hole of the outer section and which is sealingly secured to the outer section, e.g., by soldering.
German patent application Serial No. A 41 29 370 discloses a modified clutch actuating apparatus wherein the slave cyinder employs a one-piece housing made of a plastic material.
An object of the present invention is to provide a simple, compact and inexpensive apparatus for actuating friction clutches in the power trains of motor vehicles.
Another object of this invention is to provide a novel and improved slave cylinder for use in the clutch actuating apparatus.
A further object of the instant invention is to provide novel and improved connections between the constituents of the clutch actuating apparatus.
An additional object of my invention is to provide novel and improved means for centering the constituents of the clutch actuating apparatus relative to each other and/or relative to component parts of the power train.
Still another object of the invention is to construct and assemble the clutch actuating apparatus in such a way that it automatically compensates for progressing wear upon its component parts.
A further object of the invention is to provide novel and improved means for guiding the reciprocable piston of the slave cylinder in the above outlined clutch actuating apparatus.
Another object of the present invention is to provide a novel and improved housing for the slave cylinder in the above outlined clutch actuating apparatus.
An additional object of the invention is to provide novel and improved combinations of materials for the constitutents of the above outlined apparatus.
Still another object of the invention is to provide a clutch actuating apparatus which generates less heat than heretofore known apparatus.
The invention is embodied in a fluid-operated apparatus for actuating a friction clutch between a prime mover (such as an internal combustion engine) and a rotary component (such as the input shaft) in a housing or case of a change-speed transmission in the power train of a motor vehicle. The improved apparatus comprises a slave cylinder including a housing which is coaxial with the rotary component of the transmission and is borne by the transmission case, and a reciprocable annular piston which is disposed in the housing and is surrounded by a wall forming part of the housing. The apparatus further comprises a guide sleeve which surrounds the rotary component of the transmission, which is surrounded by the piston and which defines with the piston and with the wall of the housing a fluid-receiving annular plenum chamber. The sleeve includes a radially outwardly extending flange which is disposed between an end portion of the wall and an end face of the transmission case, and the apparatus further comprises means for coupling the flange to the wall. The coupling means includes a plurality of projections which are borne by the flange of the guide sleeve and are spaced apart from each other in the circumferential direction of the wall. Each projection has a first portion surrounding the end portion of the wall and a second portion which is recessed into the wall. The end portion of the wall preferably includes or constitutes a collar which is adjacent the end face of the transmission case.
The apparatus further comprises fasteners which serve to secure the housing of the slave cylinder to the transmission case. It normally or often suffices to employ a small number of (such as two) fasteners.
The plenum chamber is arranged to receive a hydraulic fluid at a pressure which can vary within a predetermined range, and the apparatus further comprises at least one seal which is provided between the housing and the guide sleeve and is arranged to withstand fluid pressures at least within the predetermined range.
Still further, the improved apparatus preferably comprises means for centering the guide sleeve relative to the housing of the slave cylinder and/or means for centering the housing and/or the guide sleeve relative to the transmission case. The latter centering means can include a portion of the guide sleeve, e.g., an annular protuberance of the flange; such protuberance is or can be surrounded and centered by an internal surface of the transmission case.
The aforementioned first and second portions of the projections of the coupling means can make oblique angles, preferably obtuse angles.
The piston of the slave cylinder has a first end portion which is nearer to and a second end portion which is more distant from the flange of the guide sleeve. A clutch release bearing is or can be mounted on the second end portion and an annular seal can be provided on the first end portion of the piston. Such annular seal is in sealing engagement with the wall of the housing of the slave cylinder as well as with the external surface of the guide sleeve.
The housing of the slave cylinder can be made in an injection molding machine of one piece with at least one nipple defining at least a portion of a path for the flow of pressurized fluid into the chamber and/or for the outflow of fluid from such chamber. It is presently preferred to make the housing from aluminum or from a plastic substance.
The guide sleeve preferably consists of a metallic sheet material. e.g., sheet steel, and can be made in a deep drawing machine.
If the housing of the slave cylinder is made of a metallic material, it is preferably a die cast product.
The wall of the housing of the slave cylinder has a preferably at least partially conical internal surface which tapers in the axial direction of the input shaft of the transmission toward the flange of the guide sleeve.
The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved clutch actuating apparatus itself, however, both as to its construction and the modes of assembling, installing and operating the same, together with numerous additional important and advantageous features and attributes thereof, will be best understood upon perusal of the following detailed description of certain presently preferred specific embodiments with reference to the accompanying drawing.